Placing self-expanding metallic, polymeric, and plastic stents or non-expanding metallic, polymeric, and plastic stents at target sites in the gastrointestinal tract and colon provides easy, safe, and effective palliation of malignant obstructions and other strictures. Indeed, where the disease in the patient becomes inoperable due to tumor extension, distant metastasis, debilitating condition, or advanced age, stents provide the better palliative treatment relative to a removable plastic tube or a removable plastic medical device intended for locations in a body.
Conventional delivery systems allow placement of stents through an endoscope working channel, beside an endoscope through a channel of an endoscope accessory device, or blind (i.e. without an endoscope). The problem is that the stent may be too large to be placed through these channels. The present invention provides, however, an alternative delivery system for the delivery of larger stents (e.g., colonic, pyloric, and the like)—where the stent is too large to be placed through the endoscope or endoscope working channel. Because the present invention works with an endoscope, it further has an advantage over placing the stent blindly.
Endoscopes
Endoscopic surgery has seen rapid growth over the past decade. A wide range of applications have been developed for the general field of endoscopes. Several applications include, by way of example only, some endoscopes that are rigid and other endoscopes that are flexible: arthroscope, angioscope, bronchoscope, choledochoscope, colonoscope, cytoscope, duodenoscope, enteroscope, esophagogastro-duodenoscope (gastroscope), laparoscope, laryngoscope, nasopharyngo-neproscope, sigmoidoscope, thoracoscope, and utererscope (individually and collectively, “endoscope”).
By way of background, a conventional endoscope has a proximal control section and, extending distally therefrom, a distal insertion portion. The terms “endoscope insert” and “insert” shall include the distal insertion portion to be inserted into a patient, whether that distal insertion portion is part of a rigid endoscope or is the elongate (long) flexible tubular section of a flexible endoscope. In addition, the terms “endoscope insert” and “insert” include any medical device such as a sheath, for example, that might be mounted onto the rigid or flexible distal insertion portion to be inserted into a patient. As is conventional, the term “distal” means away from the physician, operator, or healthcare professional (collectively, “physician”) when the device is inserted into a patient, while the term “proximal” means closest to or toward the physician or operator when the device is inserted into a patient.
The proximal control section remains outside the patient during a medical procedure and has several common features. One such feature includes a means for viewing the scene through a viewing lens disposed at the distal working insertion portion of the elongate tubular section. Other common features include a working channel for passing a tool, a light guide cable, and a power supply. For endoscopes of the flexible type, another feature may be one or more (often a pair) of articulation control knobs located at the proximal control section outside the patient for manipulating (bending and articulating) the position of the flexible distal insertion portion inside the patient's body—often, most of the flexible distal insertion portion is passively flexible, while the distal 10.0-20.0 millimeters is flexibly controlled by the articulation knobs.
The conventional endoscope further includes a light source and an image sensor for visualizing the interior of an internal region of a body. In order to form an image of the scene under observation, the light source and image sensor are located at or near the flexible distal insertion end portion of the elongate tubular section of the endoscope to be inserted into a body cavity of a patient.
The overall length and diameter of the tubular section of the endoscope may vary depending on the intended application for the endoscope. By way of example only and not by way of limitation, one embodiment according to the present invention may fit any endoscope, such as any variety of pediatric endoscope, having an outer diameter as small as approximately 5.0 millimeters. In addition, embodiments may be utilized with many sizes of endoscopes. For instance, a standard colonoscope for insertion into the colon and distal terminal ileum typically measures approximately from approximately 1,330 millimeters (“mm”) to approximately 1,850 mm in length and from about 11.1 mm to about 19 mm in diameter. The esophagogastroduodenoscope (the “gastroscope”) used for insertion into the esophagus, stomach, and duodenum may have an insertion tube with a working length that measures approximately a meter, from about 925 mm to about 1,100 mm in length, and an insertion tube diameter from approximately 5.1 mm to about 12.8 mm. An example of a longer type of endoscope is the enteroscope for insertion into the duodenum and proximal portion of the jejunum. The enteroscope may have an insertion tube that measures over 2 meters in length, from about 2,180 mm to about 2,800 mm, and an insertion tube diameter from approximately 5 mm to about 11.7 mm. A standard duodenoscope for endoscopic retrograde cholangio-pancreatography typically includes an insertion tube from about 1,030 mm to about 1,250 mm in length and from approximately 7.4 to approximately 12.6 mm in diameter. A standard choledoschoscope for passing through the channel of a duodenoscope or inserting intraductally for the bile and pancreatic ducts has an insertion tube length from about 1,870 mm to about 1,900 mm and an insertion tube diameter from approximately 2.8 mm to approximately 3.4 mm. An echoendoscope for the luminal digestive tract and adjacent organs may have an insertion tube length from about 975 mm to about 1,325 mm and an insertion tube diameter from approximately 7.9 mm to approximately 13.7 mm. An example of a shorter type of endoscope is the sigmoidoscope for the rectum and sigmoid colon. The sigmoidoscope may include an insertion tube that measures from about 630 mm to about 790 mm in length and a diameter from approximately 12.2 mm to approximately 13.3 mm.
Endoscopes may also incorporate additional functionality for observation or operation within the body, such as a working channel having an opening located at the distal end portion of the insert. Similar to the variable lengths and diameters of the different types of endoscopes, the working channels vary in diameter: gastroscope (≈2.0-6.0 mm); enteroscope (≈1.0-3.5 mm); duodenoscope (≈2.0-4.8 mm); choledochoscope (≈0.75-1.2 mm); echoendoscope (≈2.2-3.7 mm); colonoscope (≈2.8-4.2 mm); and sigmoidoscope (≈3.2-4.2 mm).
Through this working channel, the physician may pass diagnostic, monitoring, treating, or surgical tools to a site external to the distal end face of the flexible distal insertion end portion of the elongate tubular endoscope and into the observation field and working space of the physician's endoscope. For instance, stent delivery systems may be introduced through the endoscope working channel.
Stents
Minimally invasive surgical stent technology has become popular since the introduction of stents to the medical device market in the United States for vascular and cardiovascular systems, by way of example, in the early 1990s and the introduction of minimally invasive plastic tubular stents for gastrointestinal applications, for instance, since before the early 1980s. For more than a decade, stents have proven to provide an excellent means for implanting into body vessels having a passageway in order to maintain vessel patency and to reinforce, support, repair, create patency by expanding a vessel passageway, or otherwise enhance the performance of the vessel and the vessel passageway. The term “passageway” is understood to be any lumen, chamber, channel, opening, bore, orifice, flow passage, duct, or cavity for the conveyance, regulation, flow, or movement of bodily fluids and/or gases of an animal. As an example, stents have become widely accepted in the medical field for use in the passageways of a heart, blood vessel, artery, vein, capillary, bronchiole, trachea, esophagus, aorta, intestine, bile duct, ureter, urethra, fallopian tube, gastroesophageal, gastroduodenal, gastrointestinal, pylorus, colon, and other locations in a body (collectively, “vessel”) to name a few.
In general terms, a stent comprises three parts: a shaft-like tubular body (middle portion of the stent), a proximal end, and a distal end. Stents come in a variety of different configurations. In one example, a stent may further comprise a ring, or stack of rings, each ring being formed of struts and apices connecting the struts, whereby the stent defines an approximately tube-like configuration. Furthermore, the stent surface may not define a truly round cylinder if the struts are straight, because the struts follow a straight line from the apex on one end of the strut to the apex on the other end of the strut. Stents may consist of wire mesh alone (some stents are coated with substances which prevent an inflammatory response) or be cut from a tubular body to form struts and apices, and generally are eventually covered by epithelial tissue after placement within a body.
In addition to their having a variety of configurations, stents also come in different types as defined by the way they expand. For instance, the stents may be non-expanding metallic, polymeric, and plastic stents. In addition, the stents may be expandable. Various types of expandable stents have been described as self-expanding, balloon-expandable, or a combination thereof where the stent is partially self-expanding and partially balloon-expandable.
One particularly useful self-expanding stent is the Z-stent, introduced by Cook Incorporated, due to its ease of manufacturing, high radial force, and self-expanding properties. Examples of the Z-stent are found in U.S. Pat. Nos. 4,580,568; 5,035,706; 5,282,824; 5,507,771; and 5,720,776, the disclosures of which are incorporated in their entirety. The Zilver stent, introduced by Cook Incorporated, is another particularly useful self-expanding stent due to its nitinol platform and use of the Z-stent design properties. Examples of the Zilver stent are found in U.S. Pat. Nos. 6,743,252 and 6,299,635, the disclosures of which are incorporated in their entirety. By way of example only, one or more of these designs have been utilized in stents for applications involving the bronchioles, trachea, thoracic aortic aneurysms (stent-graft), abdominal aortic aneurysms (stent-graft), intestines, biliary tract, and prosthetic venous valve devices. The Z-stent and Zilver stent are capable of being compressed, inserted into a catheter or delivery device, pushed out into the passageway of a vessel, and then self-expanded to help keep the vessel passageway in an open state. A few of the embodiments of devices using one of these stents are the Zilver® 518 biliary self-expanding stent and the Zenith® AAA Endovascular Graft for the endovascular treatment of an abdominal aortic aneurysm.
In yet another embodiment, the self-expanding colonic Z-stent® by Cook provides a self-expanding tubular prosthesis used to maintain patency of malignant colonic strictures in patients having high operative risk or advanced disease. The colonic Z-stent, when fully expanded, typically measures approximately 25 millimeters (“mm”) in shaft diameter, approximately 35 mm in diameter at the flared proximal and distal ends, and from about 40 mm to about 120 mm in length from the proximal end to the distal end of the stent. The Zilver® 518 biliary stent, while not a Z-stent, is another example of a self-expanding stent.
A Z-stent and the other types of self-expanding or balloon expandable stents may be compressed to assume a resiliently collapsed tubular configuration having a smaller diameter and may be expanded to assume an expanded tubular configuration having a larger diameter. In its collapsed smaller diameter configuration, the stent may be delivered to the passageway of a vessel and expanded to the larger diameter to help keep the vessel passageway in an open state or otherwise enhance the performance of the vessel.
Delivery System
Stents are usually inserted by endoscopy or other procedures less invasive than a surgical operation, which makes the stents suitable for patients with advanced disease for whom an operation might be too dangerous. The advantages of minimally invasive stent surgery performed with the help of an endoscope are well known and understood in the medical field. As a result, there have been a growing number of devices for use with endoscopes for delivering stents into the observation field and working space of the physician's endoscope, located at the appropriate target site in the field of view, and then deployed.
Stent delivery and placement systems and tools have grown out of the need for implanting these medical devices into endovascular and other body lumens of a patient. In endoscopic and percutaneous delivery systems, a catheter or introducer sheath (collectively, “introducer”) constrains the resiliently compressed stent into a collapsed smaller diameter, carries the stent to the target site, and deploys the stent.
With conventional percutaneous (through the skin) stent delivery systems, the physician first positions a hydrophilic wire guide in the vessel passageway, usually under fluoroscopic, radiographic, or endoscopic guidance. Then, the physician inserts a catheter (or other similar percutaneous stent delivery device) over the wire guide and uses the wire guide to maneuver a portion of the delivery system through the vessel passageway and to the desired target site therein.
Depending on the target site and the medical procedure, an endoscope stent placement system may be preferred to a blind stent placement, percutaneous stent placement, or other non-endoscopic stent placement. With a conventional endoscopic stent placement system, the endoscope distal insertion portion carries the stent through any naturally body opening (e.g., the mouth, anus, urethra). The endoscopic stent placement system may comprise a rigid distal insertion portion or a flexible distal insertion portion. The physician moves the rigid distal insertion portion, or flexible distal insertion portion, of the endoscope into position at or near the target site. Then, the physician inserts the stent-carrying introducer through the endoscope working channel and out the distal opening of the working channel and into the physician's observation field and working space.
With larger self-expanding metallic, polymeric, and plastic stents and with larger non-expanding metallic, polymeric, and plastic stents, however, such as stents for colorectal, duodenal, pyloric, or other gastrointestinal or gastroesophageal diseases, to name but a few—the stent or stent delivery introducer may not be placeable through the endoscope working channel or through the endoscope accessory channel. Therefore, improved self-expanding stent delivery systems would be desirable for these larger stents.
As taught herein, the present invention relates to a delivery system that couples externally over the endoscope insert and utilizes the maneuverability and functionality of an endoscope as, so to speak, a “guide wire” to position and deploy the stent. Use of the present invention is not limited to stents, however, and the term “stent” and variants thereof shall describe embodiments according to the invention comprising other self-expanding, balloon expandable, and non-expanding implantable medical devices, such as prosthetic venous valves and other prosthetic articles for placement inside a patient's body.